Screw propeller



Oct. 25, 1949/.

3 Sheets-Sheet 1 Filed Aug. 18, 1944 w RN uw m M L, M, M m@ l W H 6 W A,-/`\N :M/ MM/ m r MN WN QN QN w W w M WN ww QN F U QN NN Nw [WML fm1.

Oct. 25, 1949.

Filed Aug. 18, 1944 L. G. FAlRHuRs-r 2,486,016

SCREW PROPELLER 3 Sheets-Sheet 2 LEONA@ G. 14121911367 'bg wm. v

3 Sheets-Sheet 3 L.` G- FAIRHURST scREw PROPELLER Oct. 25, 1949.

- Filed Aug. 18, 1944 I Patented Oct. 25, 1949 SCREW PROPELLER lLeonard Gaskell Fairhurst, -Gloucester, England, assignor to Rotol -Limited,-'Grl0ucester, England,

'a vBritish company Application August 18, 1944, SeriaLNo. 550,051 'In -Grreat Britain November 13, 1942 l2 Claims. (Cl. 170--135.27)

This inventionrelates to variable-pitch screwpropellers of the hydraulically-operated type.

Propellers rof this type at vpresent in yuse have a hydraulic `operating mechanism for changing the pitch of the blades mounted in front of and rotating with the propeller. Thi-s mechanism 1n one well-known form comprises a relatively reciprocable piston and cylinder the axially moving member of which is coupled to `each of the blades bysimple links.

Pressure-Huid, usually the engine oil, is 'conveyed tothe propeller through the hollow propeller-shaft Vwhich necessitates the use of one `or more oil tubes.

'When vthe propulsion system comprises `a pair of contra-rotating co-axial propellers Athe 'hydraulicpitch-changing mechanism is mounted on the propeller carried `by the inner shaft, 'the pitch-changing movements being transferred to the other propeller by an extension of vthe link system above referred to.

One object of this invention is to provide a simple hydraulic pitch-changing mechanism for va single propeller, or for a pair of contra-rotating co-axial propellers of the general type referred to above, which mechanism is so 'arranged 'as to enable a vclear axial space or passage to be left through the propeller-shaft.

A further object is to 'reduce the overhanging mass at the front of the propeller or propellers, this being particularly desirable in the case of vcontra-rotating co-axial propellers.

According to this invention, ina hydraulicallyoperated variable-pitch propeller-installation, the pitch-changing mechanism comprises an annular cylinder surrounding a hollow drivingshaft, uid-suppl-y-ducts communicating with it and providing a clear axial space through them and lthe driving-shaft, an annular piston in the cylinder `and means `coupling the piston to the blades to effect pitch-changing movements thereof.

According to another feature of this invention, the `fluid-supply-ducts are disposed outside the driving-shaft, and in such a construction there may be provided the combination with 'a cylinder secured on the hub of means providing a Yclear axial space through the cylinder and hub land also providing communication to each end Iof the cylinder, said means comprising a running gland of utrhich the outer surface of the cylinder forms par According to another feature of this invention, the annular cylinder may have its inner Wall spaced away from 4the shaft, in `combination with uid-supply-ducts which open yto the cylinder -through'the said inner wall.

In the case of an installation :comprising ycoaxial contra-rotating propellers, the `supply of of yf-.vorking Liluidto the cylinder may be 'delivered to it lthrough the annular space 'between the inner driving-shaft of the front lpropeller and the outer -driving-shaft'of the rear propeller, and the cuter driving-shaft may Iconstitute the inner wal-l -of the annular cylinder.

The liuid-supply-ducts maybe constituted by .a tubecr'tubes dividing ythe annu-lar space between the shaft and the inner `-wall of the cylinder for :a single propeller, or between the two shafts 'of :contra-rotating propellers into two ducts Icommunicating respectively with the -tWo ends of `the cylinder.

Inthe accompanying drawings:

vFigure 1 is a ,general arrangement viewed mainly in section showing-one form 'of thisinvention applied to Aa -co-axial centra-rotating vpropeller-installation,

Figure 2 is :a sectional detail view of a par-t of Figure 1 to a 4larger scale showing the means for supplying Working uid `to the annular cylinder, and

Figure 3 .is .a 4similar view of an 'alternative :construction .of the huid-supply means.

.Referring :.rst to Figure l, the driving shafts Afor thetwo .propellers whereof the hubs are indicated at lll, Il respectively, are indicated at I2 and I3. vIn the case lof tractor airscrews the front `one is carriedby the shaft I2 andthe vrear one by the shaft I3, but it will be appreciated that inthe case of pusher .airscrews the descriptions front and rear of the 'two .airscrews .would be inter-- changed.

The hydraulic pitch-'changing mechanism comprises a cylinder lll which is secured to the rear face of the hub I I and is of annular form, its inner wall being constituted by the outer driving-shaft I 3. Within this annular cylinder there is Vmounted a piston t5 which is connected by a suitcylindrical wall 2| of the cylinder I4 is preferably ground and a stationary housing 22 surrounds it with a iioating bush 23 arranged between them. The bush is formed towards each end with rows of suitable openings 24, 25 to provide communication with ports 26, ,2l respectively, opening into the two ends of the cylinder, and they also open into grooves 28, 29 respectively formed in the housing 22 which have suitable pipe connections 30, 3l respectively with a iiuid-pump or governorunit of the kind ordinarily used with hydraulically-operated variable-pitch propellers.

Suitable glands or packing and connections to drain are provided to deal with any leakage which may occur of the working fluid.

The cylinder may be of such axial length as will permit the piston to move over a range that will allow the blades of the propellers to be feathered and/or reversed if so desired.

When this invention is applied to a single propeller installation, a similar arrangement may be used but in this case there would be n0 inner driving shaft I2 as the propeller would be mounted on the shaft I3.

When the supply of pressure-fluid is effected in the manner illustrated in Figure 2, using the outer Wall 2l of the cylinder as part of the running gland, the rotational speed of the cylinder wall 2i, which rotates with the propeller, may be somewhat high and it is preferred to use the arrangement illustrated in Figure 3 in which the supply of fluid takes place through the inner wall of the annular cylinder. The arrangement shown in Figure 3 is applied to a two-propeller installation in which the two driving-shafts are indicated by the references i2, i3, and in this case the supply is effected through the annular space between the two shafts. For this purpose a suitable running gland conveys oil from the pump connection 32 by way of a groove 33 and openings 34 in the shaft I3 to the annular space between the shafts; two of these connections are provided spaced around the shaft, the second groove and communicating holes being shown at 35, 36 respectively. A tube 3l is provided between the two shafts to divide the space into two ducts 38, 39 respectively which communicate by ports 40, 4l with the two ends of the annular cylinder I4, the ends of the tube 37 being suitably packed to prevent leakage. It is preferred also to provide a second tube 42 to constitute one wall of the duct 39 so that it is not necessary to use the whole of the annular space between the shafts as this duct, and the packing arrangements can be considerably simplified.

If it is desired to use this arrangement with a` single-propeller-installation, the propeller would be mounted on the shaft i2 and the shaft I3 which constitutes the inner wall of the annular cylinder would be provided by a separate part which would rotate with the cylinder and receive the rotary hydraulic joints at 34, 36 for the supply of fluid.

In yet another construction, instead of dividing the annular space between the shafts I2, I3 into two co-axial ducts, there could be provided a slotted or grooved sleeve whereof the grooves communicate at one end with suitably spaced apertures in the wall of the cylinder and at the other end with a running joint of the type above referred to.

It will be seen that with any of the constructions above described, in either rsingle or twopropeller-installations there is provided a clear axial space through the propeller-shaft which permits the mounting of a gun to re through the shaft. Also there is a very considerable benefit in the disposition of the weight in` that the hydraulic cylinder is mounted between the propeller and the engine, leading to compactness and v avoidance of a large overhanging weight at the forward end of the propeller.

I claim:

1. A hydraulically-operated variable-pitch propeller installation comprising a pair of contra-rotating propellers each having a hub and a plurality of blades carried by the hub, a pair of hollow driving shafts one to carry each propeller, said shafts being concentric and spaced apart one within the other to form an annular passage therebetween, an annular cylinder arranged eX- teriorly of the propeller hubs and surrounding the outer driving shaft, a piston in said cylinder, means coupling said piston to the blades of the propellers to eiect pitch-change movements of said propellers and huid-supply ducts communieating one each with the two ends of the cylinder through the annular passage between the shafts.

2. A hydraulically-operated variable-pitch propeller installation comprising a 'pair of contrarotating propellers each having a hub and a, plurality of blades carried by the hub, a pair of hollow driving shafts one to carry each propeller, said shafts being concentric and spaced apart one within the other to form an annular passage therebetween, an annular cylinder arranged exteriorly of, and carried by the hub of one propeller and surrounding the outer driving shaft, a piston in said cylinder, :duid supply ducts connected with said cylinder through the annular passage between the shafts said iiuid supply ducts being constituted by at least one tube dividing the annular space between said driving shafts into two ducts communicating respectively with the two ends of the cylinder and means coupling the piston to the blades of said propellers to effect pitch-change movements of said propellers.

LEONARD GASKELL FAIRHURST.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,132,481 King Oct. 11, 1938 2,258,094 Keller Oct. 7, 1941 2,280,713 Martin Apr. 21, 1942 2,341,730 McNab Feb. 15, 1944 2,377,457 Stalker June 5, 1945 FOREIGN PATENTS Number Country Date 463,985 Great Britain Apr. 9, 1937 519,261 Great Britain Mar. 20, 1940 536,816 Great Britain May 28, 1941 546,291 Great Britain July 6, 1942 

